There are some creatures that sleep with eyes open due to unihemispheric sleeping - resting one brain half at a time, keeping one eye vigilant for attacks, or due to lacking eyelids!
Dolphins are marine mammals known for their intelligence and social behavior. They possess the ability to sleep with one eye open, allowing them to remain vigilant to potential threats even while resting.
1. Dolphins
Some species of penguins, particularly those living in environments with predators, have the ability to sleep with their eyes partially open to keep watch for any dangers around them.
2. Penguins
Nocturnal birds like owls often sleep with their eyes open. This behavior helps them stay alert to potential prey or threats in their surroundings.
3. Owls
Snakes actually sleep with their eyes 'open', as they don't have eyelids to close their eyes. Instead, their eyes are covered with transparent scales which protect their eyes and stop them becoming dry - these are called 'spectacles
4. Snakes
Next: The Vigilant Sleepers: Animals That Sleep With One Eye Open